The present invention relates to apparatus, systems, and methods for increasing the operability of electrical circuits at high temperatures, and more particularly for increasing the stability of state-holding circuits at high temperatures.
Boolean gates, in combination with the concept of feedback, provide the basic building blocks for modern computer memory. Typically, to convert Boolean gates into a memory device, the output of one or more of the gates is fed back into the gates' input. The result is that the new output depends on the previous output of the gates and the new output will reflect or “remember” the previous output. Because the input is typically either a high or low voltage, this type of arrangement may be used to create devices that may assume either one of two reversible and stable states. Typically, the transition from one stable state to the other is unstable. That is, during the very short period over which the transition takes place, the output of the gates may assume the same state, which state may be unpredictable.
This above-stated Boolean logic may be used to create state-holding circuits that form the most basic control and memory elements in computer and communications systems. Such state-holding circuits may include devices such as flip-flops and latches. These state-holding circuits may, in turn, be used to create devices such as registers, cache, random access memories, counters, or the like. In integrated circuits, transistors are most commonly used to implement the Boolean gates in state-holding circuits. Most transistors have a leakage current, which refers to the small amount of current that flows (or “leaks”) through a transistor when it is “turned off.” In an ideal transistor, the leakage current would be zero, but in practice, the leakage current always has some value.
Furthermore, the leakage current may vary significantly, even exponentially, as factors such as temperature and voltage increase. As temperatures continue to increase, the leakage current may increase to a point where a state-holding circuit is unreliable or fails completely. In some cases, high temperatures may cause state-holding circuits such as flip-flops to flip from one state to another. This may cause a computer system to crash or malfunction, or corrupt data stored in memory or registers. Due to this high-temperature instability, many integrated circuits are inoperable or unreliable above a rated temperature. In other cases, where a circuit may function at higher temperatures, the circuit's life span may be shortened.
The need is increasing for circuits, such as state-holding circuits, that function at higher temperatures than is currently possible. For example, in the oil and gas industry, there has been a long felt need for “smart” drill strings capable of transmitting formation data to the surface. As drilling, exploration, and electronics technology continues to improve, the feasibility of smart drill strings is becoming a greater reality. Indeed, as new oil and gas reserves may be in deeper, more remote, or harder to access locations, a greater need exists for smarter drill strings.
In order to implement a “smart” drill string, electronic components are needed to gather and transmit data along the drill string. Nevertheless, because drill stings may reach depths of 20,000 feet or more and may encountering temperatures at or near 300° C., current electronics may be inadequate, unreliable, or inoperable in downhole environments. Thus, improved electronic components are needed that are able to function in high-temperature downhole environments. Such components would also be useful in other high-temperature applications such as automotive, aviation, or geothermal applications.
Accordingly, what are needed are apparatus and methods for increasing the stability of electronic components and circuits in high-temperature environments. More specifically, apparatus and methods are needed to stabilize state-holding circuits at higher temperatures. Beneficially, such apparatus and methods would be simple and utilize currently available technology and components. Such apparatus and methods are disclosed and claimed herein.